my thoughts on science

I'm a zoologist, for most of my academic life I have only really concerned myself with animals. Even within this very broad category I have tended to focus on the feathered and furry, although insects are pretty amazing. This is a natural bias that most people probably have, but recently I have been learning more and more about plants and they are truly fascinating.

Trees, and plants in general, to me have always been the start of a much more interesting ecosystem. They are the heterotrophic instigators of nature, using the power of the sun they can make sugars and this basically gets everything going. Above that they seemed uninteresting. However, I listened to a fascinating episode of RadioLab called “From tree to shining tree” in which the details of the Wood Wide Web were unravelled into my ears. These organisms are not solitary sugar factories but part of a vast interconnected system. Below ground all trees have a symbiosis with fungi, enabling the fungi to gain glucose from the tree in exchange for water and mineral ions but each fungi doesn’t just tap up one tree for this. Instead the hyphae of the fungi link different trees, often of the same species but sometime of different species, all together into a vast network. If you have seen Avatar this might ring a bell. This connectedness allows trees to share resources with each other in times of need; for example when one member of the forest is sick or when certain species are in leaf but others are yet to be.

But why would trees want to do this? Surely if your neighbour is sick then you will be able to grow above them and gain access to the precious sunlight that they are shading you from? Well yes and no, plants do compete but trees all do better in an intact forest: low wind speeds and cool temperatures lead to reduced evaporation and more water for all, as well as reduced risk of being blown over. But they don’t just give each other glucose, they can also signal to each other about potential risk, such as insect attack or disease. The key players in these networks are the old trees, those mighty majestic mothers of the forest who are probably 500 years old, and this has implications for forest management. There is a great TED talk about this by the researcher who discovered these networks Prof Suzanne Simrad called “How trees talk to each other.”

But it isn’t just this wonderful connectedness and cooperation that has blown me away. I have been reading the book Hidden Life of Trees by Peter Wohlleben and it is a beautiful and heartfelt insight into the lives of these organisms. The book details the wonderful communication systems of trees, from emitting ethylene into the air to warn the trees around them of browsing herbivores to using pheromones to call in the predators of the specific species of aphid that are currently feeding on the tree. The book details how plants can hear water, and grow towards pipes that are running underground. How the mimosa can actually learn not to respond to a stimulus (plants can learn!!). But the part of the book that I find the most fascinating is the way in which trees create ecosystems, by slowing down the air, securing the soil, then with the host of organisms that live on, with and around them they fix nitrogen to fertilise the soil and they release volatile compounds into the air to increase rainfall. All of these ecosystem drivers occur faster and more efficiently in primary, pristine forests; again this is something that needs to be taken into account in forest management.

I recommend reading, listening to or watching any/all of these links. Truly fascinating.

One of my old colleagues, who's just finishing up his PhD has just had a paper published. James Westrip, supervised by Matt Bell, is working on interspecific communication through the pied babblers. Here's the abstract for the paper and a link to it:

Studying heterospecific communication provides an opportunity to examine the dynamics of cross-species social behaviour. It allows us to ask questions about the extent to which the transfer of information is adaptive or accidental and provides an empirically tractable context for manipulating relationships. To date, most studies of heterospecific communication have focussed on receivers. However, the selective pressures on signallers can be as important in determining the dynamics of interspecific communication. Here, we propose a simple framework for thinking about cross-species information transfer, which (i) considers whether information exchange is either accidental or adaptive and (ii) whether it is unidirectional or bidirectional. To clearly classify interactions, it is necessary to quantify all of the payoffs of interspecific communication to both signallers and receivers. This requires accurate characterisation of the currency influenced by cross-species communication (e.g. weight gain, foraging success, survival). However, quantifying the payoffs may be difficult, because each side may be benefiting via different currencies. To date, studies on heterospecific communication have focussed on only one dimension of a niche (usually antipredator or foraging signals). However, because niches are multidimensional, investigations should incorporate multiple aspects of a species’ niche, to get a better perspective on why we see certain patterns of information use between species.